Autostereoscopic 3-D displays generate imagery visible to the unaided eye. The specific characteristics of the imagery depend on the operational mechanisms of the display device, but their properties usually include: (1) appearance in front of, behind, or straddling the display, (2) visibility as three-dimensional within a range of angles or distances from the display, (3) having a perceived spatial resolution, often specified at a surface of greatest detail (e.g. the display surface if one exists), (4) responsiveness to time-varying input, e.g. capable of displaying dynamic rather than static imagery, and (5) for imagery comprised of discrete perspective views, an angular view density which, ideally, is chosen so that the reconstructed 3-D scene does not exhibit visible “jumping” from view to view during user head motion.
For context, a typical 3-D display system performs the steps of:
(a) capturing or rendering information representative of a 3-D scene and storing it in a memory subsystem as image data;
(b) providing subsets of the image data to a projection engine of the display; and
(c) optically presenting the image data as to project a 3-D image (known as reconstruction or replay).
Examples of typical 3-D displays, and approaches for performing (a) and (b), are detailed in the following references:    Halle, “Autostereoscopic displays and computer graphics,” SIGGRAPH Comput. Graph., pp. 58-62 (May, 1997);    Holliman, et al., “Three-Dimensional Displays: A Review and Applications Analysis,” IEEE Trans. Broadcasting, pp. 362-71 (2011);    Chun, et al., “Spatial 3D Infrastructure: display-independent software framework, high-speed rendering electronics, and several new displays,” in SPIE Stereoscopic Displays and Virtual Reality Systems XII, (ed. Woods et al.), Proc. SPIE-IS&T Electronic Imaging, SPIE, vol. 5664, pp. 302-312 (2005); and    J. Geng, “Three-dimensional display technologies,” Adv. Opt. Photon., vol. 5, pp. 456-535, (2013); and    Lucente, “Computational holographic bandwidth compression,” IBM Systems Journal, vol. 35, pp. 349-65 (1996).All of the foregoing references are incorporated herein by reference.
Creating 3-D imagery by projecting an image sequence synchronized to the oscillatory motion of an opto-mechanical beam-steering device, such as the lenticulars described in U.S. Pat. No. 7,864,419, is noisy, difficult to construct at scales greater than 30 cm×30 cm, and have a limited field of view. U.S. Pat. No. 7,864,419, titled “Optical Scanning Assembly,” (hereinafter “Cossairt '419”), is incorporated herein by reference. Moreover, these devices are difficult to operate in a two-axis (full parallax) scan mode because at least one mechanical axis must run at a very high frequency.
Creating static 2-D imagery in the far field has been demonstrated with a “pre-programmed” nanophotonic phased array using physically based interference modelling that requires the computation of potentially trillions of delay states to create an image of viewable size (See U.S. Pat. No. 8,988,754, and Sun, et al., “Large-scale nanophotonic phased array,” Nature, vol. 493, pp. 195-99, (2013), the entire content of each of which is hereby incorporated by reference herein for all that it discloses). However, the generation of dynamic (video) imagery using the Gerchberg-Saxton algorithm as reported is computationally expensive and requires orders of magnitude more delay-line controllers than the invention described here.
No electro-holographic or diffractive display of practical utility at a variety of scales has yet been demonstrated in the prior art. One reason for this is that the optical modulator is either too slow, or has pixels that are too large compared to the wavelength of light (resulting in imagery that either restricts head motion or requires a large output lens), or is run in a diffractive mode other than phased-array beam steering, which requires a complex scheme for asserting phase delays.
With rare exception, no autostereoscopic display technology has been of sufficient quality and utility to be widely adopted. Today's volumetric, lenticular, multi-projector, and scanned-view 3-D displays have been some combination of: unsuitably large for packaging into tablet or television form factors, uncomfortably narrow viewing angle, low image resolution at the display surface and throughout the reconstructed image volume, and computationally intensive.
Within the field of 3-D display, it is well known that 3-D imagery can be generated when light, representative of regions of a scene from a collection of viewpoints, is scanned in several directions towards a viewing region within the integration period of the human eye. This arrangement enables each eye of a viewer to potentially see a different image, which is a stereoscopic depth cue. For suitably broad fields of view, one or more simultaneous users can place their heads in different locations, inspecting a scene from various points of view.
Time-multiplexed autostereoscopic displays place demands on the frequency with which a set of light-transmitting regions must modulate, and on the number of such modulators. In one example, a 20,000 frame-per-second digital projector casts light onto a 30 cm×30 cm beam-steering array that performs oscillatory horizontal scanning at 50 Hz. In this case, the 3-D image is decomposed into 200 two-dimensional views, and the set of views are projected during each horizontal sweep of the scanner every 1/100 sec ( 1/100+ 1/100= 1/50 sec=50 Hz). Therefore, a 100×200=20,000 frame-per-second image source is required.
Workers in the field of 3-D display have experimented with various agile beam steering devices for 3-D display, such as two lenticular arrays undergoing relative vibratory motion, as described in Cossairt '419. Systems of this type have suffered from drawbacks including: narrow horizontal and/or vertical field of view, insufficient angular resolution, and acoustically noisy operation.